1. Field of the Invention
The present general inventive concept relates to a piezoelectric inkjet printhead, and more particularly, to a piezoelectric inkjet printhead having individual manifolds respectively corresponding to a plurality of pressure chambers to prevent cross-talk between the pressure chambers.
2. Description of the Related Art
An inkjet printhead is a device that prints a predetermined color image by ejecting minute droplets of ink on desired areas of a printing medium. Inkjet printheads can be generally classified into two types according to the ejection mechanism of ink droplets. The first type is a thermal inkjet printhead that ejects ink droplets using the expansion force of ink bubbles created using a heat source, and the second type is a piezoelectric inkjet printhead that ejects inkjet droplets using a pressure created by the deformation of a piezoelectric element.
FIG. 1 is a cross-sectional view of the configuration of a conventional piezoelectric inkjet printhead. Referring to FIG. 1, an ink flow channel including a manifold 2, a restrictor 3, a pressure chamber 4, and a nozzle 5 are formed inside of a flow channel plate 1, and a piezoelectric actuator 6 is formed on the flow channel plate 1. The manifold 2 is a common path for supplying ink to the pressure chamber 4 when the ink is supplied from an ink tank (not shown). The restrictor 3 is a path for supplying ink to each pressure chamber 4 from the manifold 2. The volume of the pressure chamber 4 is changed by the driving of the piezoelectric actuator 6, which causes a pressure change in the pressure chamber 4 for ejecting or receiving ink.
The flow channel plate 1 is formed by stacking a plurality of thin films which are mainly formed of a ceramic material, a metal material, or a synthetic resin material after the ink flow channel in the thin films is formed by processing each of the thin films. The piezoelectric actuator 6 is formed on the pressure chamber 4, and has a structure in which a piezoelectric film and electrodes for applying a voltage to the piezoelectric film are stacked. Accordingly, a portion of the flow channel plate 1 that forms an upper wall of the pressure chamber 4 functions as a vibrating plate 1a that is deformed by the piezoelectric actuator 6.
An operation of the conventional piezoelectric inkjet printhead having the above structure will now be described. When the vibrating plate 1a is deformed due to the driving of the piezoelectric actuator 6, the volume of the pressure chamber 4 is reduced, and as a result, ink in the pressure chamber 4 is ejected to the outside through the nozzle 5. Next, due to the driving of the piezoelectric actuator 6, the vibrating plate 1a is restored to the original position, and thus, the volume of the pressure chamber 4 increases. Due to the pressure change in the pressure chamber 4, ink enters the pressure chamber 4 from the manifold 2 through the restrictor 3.
FIG. 2 is an exploded perspective view of a conventional piezoelectric inkjet printhead which has been disclosed in Korean Patent Publication No. 2003-0050477 (U.S. Patent Publication No. 2003-0112300) by the applicant of the present general inventive concept.
The inkjet printhead of FIG. 2 has a structure in which three silicon substrates 30, 40, and 50 are stacked. Of the three silicon substrates 30, 40, and 50, a plurality of pressure chambers 32 having a predetermined depth are formed on a lower surface of the upper substrate 30. An ink inlet 31 connected to an ink tank (not illustrated) is formed through the upper substrate 30. The pressure chambers 32 are arranged in two rows on both sides of a manifold 41 formed in the middle substrate 40. A plurality of piezoelectric actuators 60 that provide a driving force to eject ink to each of the pressure chambers 32 are formed on an upper surface of the upper substrate 30. The middle substrate 40 includes the manifold 41 connected to the ink inlet 31. A plurality of restrictors 42 respectively connected to each of the pressure chambers 32 are formed on the both sides of the manifold 41. Also, the middle substrate 40 includes a plurality of dampers 43 perpendicularly formed through the middle substrate 40 at positions corresponding to each of the pressure chambers 32. The lower substrate 50 includes a plurality of nozzles 51 connected to the plurality of the dampers 43. Each of the nozzles 51 includes an ink inlet port 51a formed on an upper side of the lower substrate 50 and an ink ejection hole 51b formed on a lower side of the lower substrate 50. The ink inlet port 51a is formed in an inversed pyramid shape by anisotropic wet etching, and the ink ejection hole 51b is formed to have a predetermined diameter by dry etching.
As described above, in the inkjet printhead depicted in FIG. 2, one common manifold 41 corresponds to the plurality of pressure chambers 32. That is, the manifold 41 functions as a common flow channel to supply ink to the pressure chambers 32.
However, in the conventional piezoelectric inkjet printhead, when the pressure of each of the pressure chambers 32 is increased by the driving of the piezoelectric actuators 60, the ink in the pressure chambers 32 is ejected to the outside through the nozzles 51, and at the same time, flows back towards the manifold 41 through the restrictors 42. The ink that flows back affects other pressure chambers 32 through the common manifold 41, that is, it causes cross-talk between the pressure chambers 32. The cross-talk causes an unstable meniscus of ink in the nozzles 51 connected to adjacent pressure chambers 32, and thus, causes deviations in speed and volume of ink droplets ejected through each of the nozzles 51.